Surface Engineering for Enhanced Perovskite Solar Cells: Fullerene-Mediated Trap State Formation on CsPbI3 (001) Surface

Abstract

Photovoltaic technology, particularly perovskite materials (PSCs), has emerged as a promising avenue due to their excellent light-absorbing properties. Despite advancements, issues like the presence of defects affecting device performance persist. CsPbI3 perovskites have shown potential, but trap states induced by surface defects remain a challenge. The use of fullerene-derivatives, like C60 and PC61BM, has stand out for enhancing the device stability eliminating/reducing hysteresis and passivating trap states. However, the mechanisms behind fullerene-induced passivation of trap states and their impact on surface energetics remain unclear. This study employs periodic density functional (DFT) simulations to explore the interaction between C60, PC61BM, and CsPbI3 (001) surface, with and without defects (Cs vacancy, Pb vacancy, and I-antisite). The DFT simulations reveal that both C60 and PC61BM effectively passivate trap states induced by I-antisite defects by promoting surface reconstruction. This work contributes to understanding the fundamental aspects of surface-defect interactions in CsPbI3 perovskites. Both C60 and PC61BM play a crucial role in passivating trap states, inducing atomic reorganization, and avoiding the nonradiative recombination. The findings provide valuable insights into mechanisms for trap state passivation by fullerene derivatives, paving the way for further research to enhance perovskite solar cell performance

G.G. is thankful for the contract 2020 FISDU 00345 from the Generalitat de Catalunya and the mobility grant (MOB2021) from the Universitat de Girona. S.P.-P. appreciates the economic support of Marie Curie fellowship (H2020-MSCA-IF-2020-101020330). A.P. is a Serra Húnter Fellow and received the ICREA Academia Prize 2019. M.S. and A.P. thank the Spanish MCIN (MCIN/AEI/10.13039/50110001103) for projects PID2023-147424NB-I00, PID2020-13711 GB-I00, PGC2018-097722-B-I00, and RED2022-134331-T, and the Generalitat de Catalunya for project 2021SGR623. Computational time at the MARENOSTRUM supercomputer has been provided by the Barcelona Supercomputing Centre through a grant from Red Española de Supercomputación, projects QHS-2021-3-0009, QHS-2022-1-0016, and QHS-2022-3-0001 and also by the Consorci de Serveis Universitaris de Catalunya (CSUC). We also acknowledge the support by Baden-Württemberg through bwHPC (bwUniCluster and bwForCluster JUSTUS)